I am in awe of the periodic table. But if you stood me in front of a tank containing all the elements on the table, I would recoil in shock and horror. That's because the tank would contain not just carbon, oxygen, nitrogen, and phosphorus, but also plutonium, uranium, and every other radioactive element. At the US Hanford Nuclear Reservation in Washington State, there are 177 tanks of chemicals containing almost the whole periodic table—including 500 kg of plutonium.

Last week, the whole site—which converted uranium to plutonium for atomic bombs during the Cold War but now exclusively acts as a storage facility for nuclear waste—was put on lockdown after one of the tunnels containing highly contaminated waste collapsed. Luckily, analysis showed radioactive waste hadn't become airborne and contractors quickly filled the tunnel—one of 1,000 places in the 586 sq mile (1,500 sq km) area that is known to hold some form of nuclear waste.

Even then, the collapse made international news because Hanford experts had long expected a disaster to happen any day. The mishandling of nuclear waste at the site and the ongoing clean-up delays make Hanford one of the riskiest places on Earth. Two whistleblowers, who were employees of companies tasked with cleaning up "the most polluted site in the western hemisphere," say that Hanford could become America's Fukushima.